The present invention relates to a method for applying a brazing medium to a configuration formed of a honeycomb body disposed in a jacket pipe.
Honeycomb bodies that are made by stacking and/or winding sheet metal layers, at least some of which are structured sheet metal layers, are known in many forms. Such honeycomb bodies are used, for example, as supporting bodies for catalytically active coatings. Such coated honeycomb bodies are used, for example, as catalytic converter supporting bodies. In particular for internal combustion engines, as are used, for example, in automotive vehicles, the honeycomb bodies together with the jacket pipe form a part of an exhaust system. Different configurations of a catalytic converter supporting body are described, for example, in Published, European Patent Application EP 0 245 738 A1.
The stacked and/or wound sheet metal layers are at least partially brazed one to another, so that a monolithic honeycomb body is produced. It is known for the honeycomb body to be at least partially brazed to the jacket pipe in which it is disposed. In this case the brazing medium is introduced into the brazing areas of the metal sheets and of the jacket pipe.
Methods for applying an adhesive medium and a brazing medium to a metallic configuration formed of a honeycomb body and a jacket pipe are known, for example, from International Patent Disclosures WO 89/11938, WO 94/06594, WO 93/25339 and Published, Non-Prosecuted German Patent Application DE 29 24 592 A1.
It is known from the prior art for the honeycomb body to be at least in part provided with an adhesive medium to which a brazing powder adheres. The methods known from the prior art differ with respect to implementation of the method in the sequence of applying the adhesive medium and the brazing powder during or after the configuration of the honeycomb. A comprehensive presentation of the prior art is contained in International Patent Disclosure WO 89/11938.
The different implementations of the method with respect to the application of the brazing medium to the configuration have different advantages. The economical manufacture of the configuration is sought, however, in methods for application of the brazing medium in which the brazing medium is simply introduced into the areas in which a brazed connection is to be produced. The procedure for applying the brazing medium should be as fast as possible and done with a relatively small expenditure.
The known configuration that includes the honeycomb body disposed in the jacket pipe, is configured such that the jacket pipe projects over the honeycomb body at least in an edge section. In other words, the honeycomb body is disposed in the jacket pipe such that at least an end face of the honeycomb body is at a distance from an adjacent end face of the jacket pipe.
Such projecting edge sections of the jacket pipe form connecting areas, so the configuration can be connected to other components or elements. Thus, for example, when such a configuration is used in an exhaust system, a diffusor can be provided on one connecting area of the jacket pipe, which, for example, is connected to an exhaust pipe of an exhaust system of an internal combustion engine. It is also known for the jacket pipe to have two connecting areas, which are configured on the respective ends of the jacket pipe, wherein in these connecting areas there is substantially no honeycomb body.
Due to the previously described connecting area of the jacket pipe, transferring of the method known from the prior art for applying the brazing medium to the configuration of this type has certain disadvantages.
If the method known, for example, from Published, Non-Prosecuted German Patent Application DE 29 24 592 A1 is used for joining the honeycomb body to the jacket pipe, in which the honeycomb body together with the jacket pipe is immersed in a bath containing an adhesive liquid and is subsequently provided with powdered brazing medium, the connecting areas of the jacket pipe are also provided with the brazing medium, without this being necessary. The connecting areas are not only provided with the adhesive medium on an inside surface of the jacket pipe, but also on an outside surface of the jacket pipe. This is undesirable, as it leads to the spreading of the adhesive medium. In particular, the manipulating tools that engage with an outside surface of the jacket pipe are brought into contact with the adhesive medium. Considerable expenditure for cleaning the manipulating tools is sometimes necessary.
The methods further described in the Published, Non-Prosecuted German Patent Application DE 29 24 592 A1 are basically suitable for applying the brazing medium to the jacket pipe and to the honeycomb body, wherein these methods for applying the brazing medium are relatively costly.
It is accordingly an object of the invention to provide a method for applying a brazing medium to a configuration that overcomes the disadvantages of the prior art methods of this general type, which makes efficient production of the configuration possible.
In order to apply the brazing medium to the configuration which includes the honeycomb body and the jacket pipe, it is proposed that the honeycomb body is first constructed by stacking and/or winding sheet metal layers, at least some of which are structured sheet metal layers, such that it has channels which can conduct a fluid flow. The honeycomb body is partially introduced into the jacket pipe. The section of the honeycomb body projecting from the jacket pipe is brought into contact, with its end face, with an adhesive liquid. Afterwards the honeycomb body is introduced in the jacket pipe and the brazing medium is introduced into the honeycomb body.
Because only the section of the honeycomb body projecting out of the jacket pipe is brought into contact with the adhesive liquid, the jacket pipe is prevented from also coming into contact with the adhesive liquid. In this way, the jacket pipe is free of the adhesive medium, whereby the brazing powder does not adhere to the jacket pipe.
Because the jacket pipe is not provided with the adhesive medium, it is unnecessary to optionally free the jacket pipe from the adhesive medium in order to prevent the spreading of the adhesive medium.
Because the section projecting from the jacket pipe is brought into contact with the adhesive medium, whereby the honeycomb body is at least in part provided in its axial direction with the adhesive medium, the honeycomb body is also provided with the adhesive medium over its entire cross-sectional surface. Therefore, even edge areas of the honeycomb body can be provided with the brazing powder without any problems. In this way it is guaranteed that a reliable brazed joint can be configured even in the edge area of the honeycomb body and respectively between the honeycomb body and the jacket pipe.
According to a further advantageous feature of the method, it is proposed that prior to the application of the brazing medium, a section of the honeycomb body opposite the section is brought into contact with the adhesive medium. In particular with the configuration which has the jacket pipe, wherein the jacket pipe has a connecting area on each of the opposite ends, it is proposed that the honeycomb body is pushed through the jacket pipe so that one section projects out of the jacket pipe. This section is brought into contact with the adhesive liquid. After the honeycomb body is introduced in the jacket pipe such that the honeycomb body does not substantially lie in the connecting areas of the jacket pipe.
For stable handling of the configuration, it is proposed that the honeycomb body is introduced into the jacket pipe such that while one or the other section is brought into contact with the adhesive medium, the honeycomb body is located, over a substantial part of its axial length, in the jacket pipe. In this way, the configuration has an advantageously positioned center of gravity that prevents the configuration from toppling over.
In particular it is proposed that the honeycomb body is introduced in the jacket pipe such that it projects at least 1 mm, preferably 5 mm, out of the jacket pipe. This extent is sufficient to prevent the jacket pipe from also coming into contact with the adhesive medium.
The honeycomb body and the jacket pipe have different thermal expansion behavior. It has therefore been sought to avoid having a rigid connection between the respective end areas of the honeycomb body. If there are no rigid connections in the respective end areas of the honeycomb body with the jacket pipe, thermal stresses between the jacket pipe and the honeycomb body are avoided. It is already known per se from International Patent Disclosure WO 96/26805 how such thermal stresses can be avoided by suitable brazing of the honeycomb body to the jacket pipe. According to an advantageous configuration of the method according to the invention, thermal stresses between the honeycomb body and the jacket pipe are avoided in that a sleeve-shaped element is introduced in the jacket pipe. The sleeve-shaped element has an outside jacket which comes substantially into contact with a part of the inside jacket surface of the jacket pipe, and in which the honeycomb body is disposed. Brazing of the honeycomb body to the jacket pipe is prevented by this sleeve-shaped element. The sleeve-shaped element simply extends over a part of the axial extent of the jacket pipe and of the honeycomb body. The sleeve-shaped element is preferably formed as a foil.
Because of the manufacturing technology, the jacket pipe is somewhat out-of-round. There are also tolerances with respect to the variations of an internal diameter of the jacket pipe. Due to this, a gap forms between the internal jacket surface of the jacket pipe and the element. Because the honeycomb body is brought into contact with the adhesive medium when projecting out of the jacket pipe, the adhesive medium is prevented from getting into the gap between the element and the jacket pipe.
Therefore, the gap also remains substantially free of brazing medium after the brazing medium is applied. In this way it is also ensured that there is no brazed connection between the jacket pipe and the sleeve-shaped element. On the other hand, it is also ensured that the honeycomb body can also be brazed as far as the sleeve-shaped element and also to the sleeve-shaped element.
Preferably, the sleeve-shaped element is connected to the jacket pipe such that when the honeycomb body is placed in the jacket pipe, the sleeve-shaped element stays in a pre-determined position even though the honeycomb body, which is pressed in the axial direction and as a consequence the sleeve-shaped element also is, and because of this exerts a force upon the sleeve-shaped element in the direction of introduction of the honeycomb body. In particular it is proposed that the element is materially joined to the jacket pipe. This can, for example, be a welded connection. Alternatively, or in addition, the element can be glued to the jacket pipe. The connection between the sleeve-shaped element and the jacket pipe is preferably made such that the strength of the connection is less than the strength of a connection between the element and the honeycomb body. In particular with the adhesive bonding of the element and the jacket pipe, this can be increased during a brazing process because of the temperatures prevailing during the brazing process. Because the connection between the element and the jacket pipe is not as strong as the connection between the element and the honeycomb body, it is also ensured that thermal stresses between the jacket pipe and the honeycomb body are not conducted due to the element into the honeycomb body. Preferably, the element is manufactured from the same material as the honeycomb body and/or the jacket pipe. The connection between the element and the jacket pipe is substantially an assembly connection by which it is ensured that during assembly, that is to say during introduction of the honeycomb body in the jacket pipe, the element does not change its position.
In order to braze the honeycomb body in an axial portion of the jacket pipe and with the sleeve-shaped element, it is proposed that at least one brazing section is configured which overlaps the honeycomb body and the element. This is preferably a brazing section closed when viewed in the direction of the periphery of the jacket pipe.
According to a further advantageous feature of the method, it is proposed that the section to be wetted with the adhesive medium is brought into contact with an applicator device which contains the adhesive medium. Whereby the applicator device is provided with a wetting surface which is larger than an end face of the section, and completely overlaps it. By this advantageous further development of the method, it is ensured that the section of the honeycomb body can be brought into contact over its entire cross-section with the adhesive medium. The advantage of this implementation of the method is also in that the same applicator device can be used for wetting honeycomb bodies that have different cross-section areas. It is therefore unnecessary to match the applicator device to different cross-sectional geometry of honeycomb bodies.
Advantageously, the configuration is substantially brought into contact with the adhesive medium in a vertical position, that is to say the longitudinal axis of the honeycomb body is substantially vertical. The applicator device can be disposed below the honeycomb body, for contacting the section of the honeycomb body. An implementation of the method is preferred in which the applicator device is disposed above the jacket pipe and the section is brought into contact with the applicator device.
With such a configuration of the applicator device, the adhesive medium also flows into the section due to gravity. Depending on the contact time of the section with the applicator device, and/or on the dwell time of the honeycomb body in this vertical position, it can be ensured that the adhesive medium is introduced into it over the entire axial length of the honeycomb body or over a part of the axial length of the honeycomb body. In order to provide the honeycomb body in areas relevant to a brazed connection with the adhesive medium, it is not necessary for them to remain for a correspondingly long time on the applicator device. It is sufficient when the section remains in contact with the applicator device, in particular with the adhesive medium, for as long as sufficient adhesive medium gets into the individual channels of the honeycomb body, so a sufficient wetting of the areas relevant for configuring a brazed connection takes place. By the implementation of the method, it is also no longer necessary to bring the honeycomb body into contact with the adhesive medium on both sides. In particular, the time which is necessary for transporting the configuration from a wetting point in which the adhesive medium is introduced into the honeycomb body, to the brazing medium application point, in which the brazing powder is introduced into the honeycomb body, is used for automatic transport of the adhesive medium inside the honeycomb body when the honeycomb body is transported in its vertical position.
In particular with the application of the adhesive medium by an applicator device disposed above the honeycomb body, it is advantageous that the adhesive medium carrier is configured to be substantially elastic and absorbent. If, for example, the section is pressed against the adhesive medium carrier that contains the adhesive medium, it is ensured that the adhesive medium leaves the adhesive medium carrier and it enters into the section. It is also possible to press the adhesive medium carrier against the section of the honeycomb body.
Alternatively, the configuration and the adhesive medium carrier can be moved relatively to one another such that they press against one another.
When there is a serial application of the brazing medium, the individual honeycomb bodies are successively brought into contact with the adhesive medium carrier. If the honeycomb bodies are pressed against the adhesive medium carrier, there is the risk that due to material fatigues the adhesive medium undergoes a structural breakdown which can lead to an insufficient introduction of the adhesive medium in the section. This can lead to an insufficient adhesive medium being made available, on which the brazing powder adheres to. In order to ensure that a sufficient adhesive medium can be introduced into the section of the honeycomb body, it is proposed that contact surfaces occurring during a contact of the section with the adhesive medium carrier or with the adhesive medium, only a partially overlap occurs during at least two successive configurations. This proposal is based on the consideration that the adhesive medium carrier is not contacted on the same places by successive configurations, whereby the adhesive medium carrier is, at least partially, not stressed in the same places, so material fatigue of the adhesive medium carrier cannot occur, or only with great delay.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for applying a brazing medium to a configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.